You have to have something to hook up the new drive. Here is a less expensive option for the external drive especially if you will not need it but for moving your data.http://eshop.macsales.com/item/Newer%20T...
Then download a free application called SuperDuper:
http://www.shirt-pocket.com/downloads/SuperDuper!.dmg
Hook the drive up with the adapter and clone your data. Then to install the drive, here’s the guide: http://www.ifixit.com/Guide/Repair/Installing-MacBook-Pro-15-Inch-Core-2-Duo-Model-A1211-Hard-Drive-Replacement/459/1